In Jordan, a ‘stunning’ discovery under Petra’s ancient stone

We can't be certain about anything Jesus said but it's possible that some of the sayings attributed to him in the Gospels are roughly accurate. There are a lot of similarities between the Gospels, of course, and one of the theories put forward to explain some of the similarities is that several of the Gospel writers had access to a book, since lost, which consisted entirely of sayings attributed to Jesus, and that book was perhaps written by someone who followed Jesus around writing down some of what he said. Unfortunately, even if the words are quoted roughly accurately in some cases that doesn't really tell us what Jesus meant by them because a lot of context has been lost and the Gospel writers may have quoted rather selectively from the material they had access to.

Yes, that is the 'Q' source theory. However this is a very questionable theory.

When you have A and B that look pretty much the same. Then its much more likely that B simply copied from A, or A from B.

If you want to introduce a new source C (or in this case Q), then you need to have good evidence for why the other options were not picked. In case of the 'Q' source this isn't really the case.

The are multiple things that the Q source can't really explain. The modern reference book on this topic is 'The Case Against Q: Studies in Markan Priority and the Synoptic Problem' if you are interested in that. There are just really big problems with the concept.

And even if 'Q' existed, its not really good evidence for it being the word of Jesus. We know for a fact that 'sayings of X famous person' were a common thing back then. We have 'Gospel of Thomas' that is likely a later version of that. We have this today with Quotes from people like Theodore Roosevelt or Abraham Lincoln. Any interesting sounding saying is simply attributed to whoever person.

So we have a potential source that we have 0 evidence of and no text that even references such a source. And then we have plenty of evidence that if it existed, it likely wouldn't say what people want it to say, because so maybe an earlier source existed but its a huge stretch to then say 'therefore this source was written by somebody who heard these things first hand'.

The idea that it is 'quotes' is simply because the majority of the things 'Matthew'/'Luke' insert into 'Mark' was speeches. I do think for sure earlier sources existed, maybe even earlier gospels. But we just don't have them (as far as we can tell).

I also think the actual reality is more complex then all the simple solution to the 'Synoptic Problem'. Reality all these scripts were revised over and over. And I think good recent work is being done on properly attributing the Gospels from Marcion original 'New Testament'. Marcion is critical in 'New Testament' development but very much understudied because he is a 'heritic'. The Gospel of 'Luke' is likely a strongly revised version of the gospel that was in Marcion. And potentially that version predates even 'Mark' but that is up for debate. Markus Vinzent is really great on this topic if you are interested.